Semiconductor chip having a low-noise ground line

ABSTRACT

A semiconductor chip has a first ground line for maintaining a stable ground potential for the internal circuit. The first ground line is connected to a second ground line disposed on a scribe region of the semiconductor chip via a bonding pad, which is connected to an external lead frame. I/O circuit has a third ground line directly connected to the second ground line without passing the bonding pad. The noise propagated from the third ground line to the first ground line is reduced by passing the noise through the bonding pad.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a semiconductor device having alow-noise ground line and, more particularly, to a structure forreducing the noise propagating through the ground line in asemiconductor device.

(b) Description of the Related Art

A semiconductor device generally has a pair of source lines including ahigh voltage source line and a ground line for supplying electric powerto the functional elements disposed therein. Referring to FIG. 1 whichshows a schematic top plan view of a first conventional semiconductorchip, the semiconductor chip is implemented as a SRAM device and formedon a p-type silicon substrate. The semiconductor chip 10 has a scriberegion 12 on the outer periphery of the chip 10, wherein a ground line13 shown by hatching is disposed. In the internal area of thesemiconductor chip 10, another ground line 14 shown also by hatching isdisposed for supplying a ground potential to the functional elements inthe internal area. Both the ground lines 13 and 14 are connectedtogether through bonding pads 14A and 14B.

A high voltage source line 15 is disposed in the internal area forsupplying a source potential to the internal circuit, and connected toan external lead frame (not shown) through bonding pads 15A and 15Bdisposed at the ends of the source line 15, by using a bondingtechnique. The ground lines 13 and 14 are also connected to the externallead frame through bonding pads 14A and 14B disposed at the ends of theground lines 13 and 14, by using a bonding technique.

I/O circuit 16 is disposed as a part of the internal circuit adjacent tothe scribe region 12 of the semiconductor chip 10. The I/O circuit 16includes a plurality of output transistors 19A to 19F, which areconnected to a common ground line 17 for the I/O circuit 16, source line18 and corresponding signal lines not shown in the figure. The signallines are connected to the external lead frame through bonding pads by abonding technique for outputting corresponding signals from the outputtransistors. The ground line 17 and the source line 18 are connected tobonding pads 17A and 18A, respectively, which are connected to externallead frame for receiving the ground potential and the source potential.

With the recent increase in the operational speed of the semiconductordevice, it has become difficult to obtain a stable operation of thesemiconductor chip of FIG. 1 due to the adverse effect of the noisereflected during signal transmission from the output transistors. Forreducing the adverse effect, it may be required that the ground line 17disposed for the output transistors 19A to 19F have a larger width forsuppressing the fluctuation of the ground potential on the ground line17. However, the demand for reduction of the chip size for thesemiconductor device in the recent years prevents a large width for theground line 17, which leads an unstable operation of the semiconductordevice.

Referring to FIG. 2 which shows a top plan view of a corner portion of atypical DRAM formed on an n-type semiconductor substrate as a secondconventional semiconductor chip 20, a first stage circuit block 25 as apart of the internal circuit is disposed in vicinity of the outerperiphery of the semiconductor chip, wherein ground lines 23 and 24extend parallel to each other. FIG. 3 shows a circuit configuration forthe input stage circuit block 25 shown in FIG. 2, wherein p-channeltransistors Q1 and Q2 and an n-channel transistor Q3 are connected inseries between a high voltage source line Vcc and the ground line. Anaddress terminal connected to the gates of transistors Q2 and Q3 isconnected to the bonding pad 27A through the electrostatic dischargeelement 26A as shown in FIG. 2. If another address terminal is disposedin the first stage circuit block 25, the another address terminal issimilarly connected to the bonding pad 27B through the electrostaticdischarge element 26B as shown in FIG. 2.

The bonding pads 27A and 27B are respectively connected to the externallead frame by a bonding technique for connecting the address terminalsto the external lead frame. The electrostatic discharge elements 26A and26B are connected to the ground line 24 for protecting the semiconductordevice against destruction of the transistors caused by theelectrostatic discharge failure. The ground line 23 disposed on thescribe region 22 is connected to the ground line 24 through a bondingpad 24A, which is connected to the external lead frame by a bondingtechnique. In FIG. 2, the recent increase in the operational speed ofthe semiconductor device also causes the ground potential of the groundline 24 to fluctuate due to the noise on the ground line 24.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the present invention toprovide a semiconductor device wherein fluctuation of the groundpotential and/or the source potential of the semiconductor device can besuppressed.

The present invention provides, in a first aspect thereof, asemiconductor chip comprising a semiconductor substrate including aninternal circuit region and a scribe region encircling the internalcircuit region, the internal circuit region receiving therein aninternal circuit and an I/O circuit for inputting an external signal tosupply an internal signal to the internal circuit, a first source linedisposed in the internal circuit region for applying a first potentialto the internal circuit, a second source line formed on the scriberegion and connected to the first source line via a bonding pad forapplying the first potential to the semiconductor substrate, and a thirdsource line connected to the second source line without passing thebonding pad for applying the first potential to the I/O circuit.

The present invention provides, in a second aspect thereof, asemiconductor chip comprising a semiconductor substrate including aninternal circuit region and a scribe region encircling the internalcircuit region, the internal circuit region receiving therein aninternal circuit and an I/O circuit for inputting an external signal tosupply an internal signal to the internal circuit, a first source linedisposed in the internal circuit region for applying a first potentialto the internal circuit, a second source line formed on the scriberegion and connected to the first source line via a bonding pad forapplying the first potential to the semiconductor substrate, the firstsource line having a first portion directly connected to the I/O circuitand to a second portion of the second source line without passing thebonding pad.

In accordance with the semiconductor devices of the present invention, aground line or high voltage source line disposed for the internalcircuit as one of the source lines is less susceptible to noisegenerated by the I/O circuit, whereby a stable operation of thesemiconductor chip can be obtained.

The above and other objects, features and advantages of the presentinvention will be more apparent from the following description,referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a first conventional semiconductor chip;

FIG. 2 is a partial top plan view of a second conventional semiconductorchip;

FIG. 3 is a circuit diagram of the first stage circuit block shown inFIG. 2:

FIG. 4 is a top plan view a semiconductor chip according to a firstembodiment of the present invention;

FIG. 5 is a partial top plan view of a semiconductor chip according to asecond embodiment of the present invention; and

FIG. 6 is a sectional view of the semiconductor chip of FIG. 5 takenalong line VI—VI in FIG. 5.

PREFERRED EMBODIMENTS OF THE INVENTION

Now, the present invention is more specifically described with referenceto accompanying drawings, wherein similar constituent elements aredesignated by similar reference numerals or related reference numeralsthroughout the drawings.

Referring to FIG. 4, a semiconductor chip according to a firstembodiment of the present invention is implemented as a SRAM deviceformed on a p-type silicon substrate. The semiconductor chip 10 has onthe outer periphery of the semiconductor chip 10 a scribe region 12,whereon a first ground line 13 shown by hatching is disposed. The scriberegion 12 is generally used for dicing a semiconductor wafer to separatethe semiconductor chip 10 from other semiconductor chips. Thesemiconductor chip also has an internal circuit region encircled by thescribe region 12, and a second ground line 14 shown by hatching anddisposed for supplying a ground potential to the functional elements inthe internal circuit region. Both the first and second ground lines 13and 14 are connected together through bonding pads 14A and 14B toimplement one of a pair of source lines.

A high-voltage source line 15 as the other of source lines is disposedin the internal circuit region for supplying a high voltage potential tothe internal circuit, and connected to an external lead frame (notshown) through bonding pads 15A and 15B disposed at the respective endsof the high voltage source line 15, by using a bonding technique. Theground lines 13 and 14 are also connected to the external lead framethrough the bonding pads 14A and 14B disposed at the ends of both theground lines 13 and 14, by using a bonding technique.

An I/O circuit 16 including a plurality of output transistors 19A to 19Fis installed adjacent to the scribe region 12, wherein each transistorin the I/O circuit 16 is connected to a third ground line 17, a highvoltage source line 18 and corresponding signal lines (not shown). Thesignal lines are connected to the external lead frame through respectivebonding pads by a bonding technique for outputting corresponding signalsfrom the output transistors 19A to 19F. The third ground line 17 and thehigh voltage source line 18 are connected to bonding pads 17A and 18A,respectively, which are connected to the external lead frame forreceiving the ground potential and the source potential, respectively.

The third ground line 17 disposed for the I/O circuit 16 and connectedto each output transistor is directly connected to the first ground line13 through wires 71 to 77 disposed for respective output transistors 19Ato 19F, without passing the bonding pads 14A and 14B. The directconnections of the third ground line 17 to the second ground line 13 onthe scribe region 12 allow the improvement of the function of the thirdground line 17 for maintaining a stable ground potential of the I/Ocircuit 16. In this configuration, noise generated on the third groundline 17 by the I/O circuit 16 is not directly transferred to the secondground line 14 for the internal circuit, whereby the magnitude of thenoise transferred from the third ground line 17 to the first ground line14 is reduced by the bonding pads 14A and 14B connected to the externallead frame.

Referring to FIG. 5, a semiconductor chip according to a secondembodiment of the present invention is shown in a partial top plan viewthereof. In the illustrated configuration, a first ground line 23 isdisposed on the scribe region 22 for applying a ground potential to thesemiconductor substrate. Adjacent to the first ground line 23, a secondground line 24 extends parallel to the first ground line 23 and isconnected to the first ground line 23 via a bonding pad 24A, which is inturn connected to an external lead frame.

An I/O circuit including a first stage circuit block 25 for receiving anexternal signal is disposed adjacent to the second ground line 24. Thefirst stage circuit block 25 has a circuit configuration shown in FIG.3, wherein the source of the n-channel transistor Q3 is electricallyconnected to the second ground line 24. The address terminal 40 of thefirst stage circuit block 25 is connected a bonding pad 27A through anelectrostatic discharge element 26A. Another address terminal of thefirst stage circuit block 25, if any, is also connected to a bonding pad27B through another electrostatic discharge element 26B. The bondingpads 27A and 27B are respectively connected to the external lead frameby a bonding technique. The electrostatic discharge elements 26A and 26Bare connected to the second ground line 24 for discharging theelectrostatic charge entering to the semiconductor chip 20 through theaddress terminal 40, thereby protecting the semiconductor chip 20against an electrostatic discharge failure.

In the present embodiment, the second ground line 24 disposed for thefirst stage circuit block 25 and the first ground line 23 disposed onthe scribe region 22 are formed as a single line in the region adjacentto the first stage circuit block 25 by interposing therebetween aplurality of line segments 241 so that a plurality of slits or apertures242 are formed between each adjacent two of the line segments 241. Theconnection of the first ground line 13 and the second ground line 14 inthis configuration also allows a stable ground potential of the secondground line 24 for the internal circuit even in the case of a higheroperational speed of the semiconductor device.

In some instances, a dicing operation of the semiconductor wafer into aplurality of chips along the scribe region 22 involves a crack in thefirst ground line 23 formed on the scribe region 22 due to the stresscaused by the dicing. The slits 242 formed between the first ground line23 and the second ground line 24 according to the present embodimentprevent the crack generated on the first ground line 23 from extendingtoward the second ground line 24 for the first stage circuit block 25 ofthe internal circuit block. Exemplified dimensions of the ground linesare such that: the distance between the slits 242 is 100 μm, the lengthand width of the slits 242 are 100 μm and 7 μm, respectively, the widthsof the first and second ground lines 23 and 24 are 10 μm and 5 μm,respectively.

Referring to FIG. 6, there is shown a cross-sectional view of thesemiconductor chip 20 taken along line VI—VI in FIG. 5. Thesemiconductor chip 20 is formed by the steps including forming a fieldoxide film 32 on a p-type semiconductor substrate 31, forming aninterlayer dielectric film 33 thereon, forming the second ground line 24for the first stage circuit block as well as the first ground line 23 onthe dielectric film 33 and the scribe region 22 of the semiconductorsubstrate 31, and forming a cover film made of SiON on the precedingfilms.

The first ground line 23 on the scribe region 22 functions for applyinga ground potential to the semiconductor substrate 31. If thesemiconductor substrate 31 is of n-type, the first ground line 23 isreplaced by a high voltage source line formed on the scribe region 22and connected to an external source line Vcc and the drain of thep-channel transistor Ql shown in FIG. 3. In this case, the high voltagesource line has a stable source potential according to the presentinvention.

Since the above embodiments are described only for examples, the presentinvention is not limited to the above embodiments and variousmodifications or alterations can be easily made therefrom by thoseskilled in the art without departing from the scope of the presentinvention.

What is claimed is:
 1. A semiconductor chip comprising a semiconductorsubstrate including an internal circuit region and a scribe regionencircling said internal circuit region, said internal circuit regionreceiving therein an internal circuit and an I/O circuit for inputtingan external signal to supply an internal signal to said internalcircuit, a first source line disposed in said internal circuit regionfor applying a first potential to said internal circuit, a second sourceline formed on said scribe region and connected to said first sourceline via a bonding pad for applying said first potential to saidsemiconductor substrate, a third source line connected to said secondsource line without passing said bonding pad for applying said firstpotential to said I/O circuit, and a plurality of fourth source linesdirectly connected to said second source line, wherein said I/O circuitincludes a plurality of transistors each connected to a correspondingone of said fourth source lines.
 2. A semiconductor chip as defined inclaim 1, wherein said bonding pad is connected to an external leadframe.